Stent grafts are used for treatment of vasculature in the human or animal body to bypass a repair or defect in the vasculature. For instance, a stent graft may be used to span an abdominal aortic aneurism. In many cases, however, such damaged or defected portion of the vasculature may include a branch vessel such as a mesenteric artery or a renal artery. Bypassing such an artery without providing blood flow into the branch artery can cause problems and hence it has been proposed to provide a fenestration in the wall of a stent graft which, when the stent graft is deployed, is positioned over the opening to the branch vessel. Another stent graft can be deployed through the fenestration into the branch vessel to provide a blood flow path to the branch artery.
A problem exists, however, in mapping the vasculature so that a fenestration is positioned correctly in relation to the branch vessel when a stent graft is constructed. Where the position of a fenestration with respect to a branch vessel is offset when the stent graft is deployed, it may be difficult to deploy guide wires and catheters from the stent graft into the branch vessel to enable correct positioning of the branch vessel stent graft. Also when the fenestration is offset from the branch and a stent graft is deployed into the branch vessel from a main stent graft, the branch vessel stent graft may be kinked to such an extent that blood flow will not occur through it.